1. Field of the Invention
This invention relates generally to covers for gondola railroad cars, and more specifically to slidable covers which provide essentially a watertight enclosure for the contents of the gondola type railroad car.
2. Background Art
Gondola railroad cars having walls extending upwardly from a horizontal base of a railroad car truck body are utilized for carrying various goods, including finished steel goods. For long trips, during which good weather cannot be anticipated, it has been found advantageous to cover the top of the gondola car so that rain or snow does not come into contact with the goods being shipped. Contact with the elements causes deterioration of certain goods which may be carried in gondola railroad cars, to the detriment of the quality of the goods. For example, coils of rolled steel sheets, for which long distance transportation gondola railroad cars are preferred, contact with the elements such as snow or rain may cause deterioration of the steel sheet coils, and may render portions of the rolled steel sheet coils useless for their intended purpose.
Protecting the load in a gondola car is thus necessary for the transported goods to be delivered in a useful shape. One known method in the railroad industry to accomplish this goal is to provide solid covers, made of metal, which cover one-half of the gondola car. Two of these covers are capable of providing a fluid-tight cover of the well of the gondola car, so that the contents are protected from the elements. While such covers provide excellent protection from the elements, essentially sealing the gondola car's interior, the removal and replacement of the gondola car solid metal covers is a time, energy and resource consuming process. These types of covers are typically made from solid metal, and weigh upwards of several thousand pounds each. The covers normally require cranes to attach onto a looped handle structure on the top of the cover and to lift each cover so that it may be temporarily stored beside the gondola car. It is normally possible to use the same cranes with which the rolled steel coils are loaded and unloaded. However, several disadvantages result from utilizing such solid metal gondola car covers.
First, space in a loading and unloading zone must be allocated beside the gondola railroad car for temporary storage of the massive gondola car covers. Space is usually very limited in a loading zone, for example, for loading steel coils, and the covers must be usually stored for at least 4-8 hours in a zone where space may be desirable for other activities.
The amount of time and energy expended in removal and replacement of the gondola car covers can vary depending upon the equipment used and on the skill and experience of the operators. However, an average amount of time of at least 8 hours may be expended in the loading zone devoted only to the task of removing and replacing the solid covers. When factoring in the time expended to also load or unload the rolled steel coils from the gondola car, the operation may require one full day for loading, and a second full day in unloading the coils. Moreover, if a string of cars must stand for loading or unloading, space requirements do not permit loading or unloading more than two gondola cars per day, requiring up to a week for loading a full train.
Because of recent EPA regulations, the trucking industry has also found need to r cover truckloads quickly, efficiently and without large expenditures of resources. For example, tarps have long been known and used to cover trucks with walled sides, which trucks may be used to carry loose loads, such as gravel or fly ash. These tarps must be tied down along the lengths of the truck on each side, which operation requires two persons, one to tie down the tarp on each side of the truck. This procedure has been found to be inefficient, time consuming and requires the services of at least two people.
To overcome this inefficiency, the trucking supply industry has developed tarpaulin extension systems which can be manually operated by a single operator. For example, U.S. Pat. No. 4,858,984 describes and illustrates such a slidable truck cover assembly for use with open bed trucks. The slidable truck cover assembly utilizes a series of pulleys and a looped cable attached to a movable tarpaulin, sometimes referred to as a tarp. The tarp rests on and may be connected to a plurality of slats, which are movable along the top of the truck walls, so that the tarp has a base upon which to rest, and to keep the tarp from coming into contact with the load.
While sufficient for purposes of a regulation size truck, the assembly taught in U.S. Pat. No. 4,858,984 cannot be used in much larger railroad car constructions. It has been found that a railroad car using such a tarp when moving at high speed, or if there is a cross-wind, causes air flows under the tarp, lifting it up above the top wall of the railroad car and creating a tunnel effect for the wind to blow through and disturb the loose load. Additionally, the much greater longitudinal length of a railroad car requires a system for moving, extending and retracting the tarp which is not subject to excessive frictional forces, so that the tarp extension retraction operations may be efficiently completed by a single operator.
Retractable covers specific for use on railroad cars is illustrated and described in U.S. Pat. No. 5,026,109 to Merlot, Jr. The segmented cover system utilizes a plurality of solid cover sections which are nestable over each other and which are extended and retracted by means of a pulley and cable system, similar to that shown in aforementioned U.S. Pat. No. 4,858,984. However, the molded solid cover sections, including durable material compositions, such as polyurethane, are expensive to manufacture, assemble and maintain.
For these reasons, what is needed in the railroad industry is an inexpensive, efficient railroad car cover assembly which can be utilized by a single operator on the ground, and which can deploy or retract a cover over the full length of a railroad car in a minimum amount of time, on the order of five minutes, rather than hours.